Truck and trailer bodies and large shipping containers typically utilize pivoted doors at one end wall to facilitate loading and unloading of the containers. Various door control mechanisms are used with such doors for latching and maintaining the doors in a closed position and to reduce or eliminate the transverse distortion, or racking, in the trailer bodies and cargo containers.
In the past, these mechanisms have included one or more shafts or lock rods which extend the height of the door and have latching cam members at each end which are engageable with keeper members on the door frame. Anti-rack mechanisms of this type are typically provided with cam members that extend laterally from opposite sides of the lock rod for latching the doors, aligning the doors relative to the door frame and resisting racking. Constructions of this type are illustrated in U.S. Pat. Nos. 3,099,473, 3,484,128 and 3,695,661. The cam members disclosed include forked portions and cam surfaces engageable with opposite portions of the keeper member.
Prior mechanisms of this type have sometimes been provided with latch members that are universal so that only one cam and keeper need be manufactured for use at either end of the shaft and on doors pivoted at either side of the frame.
As the size of truck trailers and cargo containers has increased, a combination of changes has been made in the configuration of trailers and containers, including greater trailer length and larger door openings. Enlargement of the door openings has been achieved by narrowing the associated door frames housing the doors. One problem with the enlarged sizes of the trailers and doors has been the increased racking effect on the containers. The reduced size of door frames has also reduced the surface area of the frame which is available for attachment of the keeper members. This in turn has diminished the vertical height available for the cams and keepers and has thereby limited the amount of door misalignment that can be corrected by the inclined camming surfaces of the latch members, particularly because any one cam surface extended only a small portion of the cam height.